package javax;

public class Demo {
    class ListNode{
        int val;
        ListNode next;
        public ListNode(int x){
            val = x;
        }
    }
    public ListNode A(ListNode head){
        if (null == head){
            return head ;
        }
        ListNode temp = new ListNode(100);
        ListNode node = null;
        temp.next = head;
        if (null == temp){
            node = temp;
            node.next = node;
            temp = temp.next;
        }else {
            node = temp;
            node.next = node;
            temp = temp.next;
        }
        return head;
    }
}
